Pattaramon Chanbua has denied that Chinese-born Wendy Farnell, who has so far been portrayed as the child's biological mother, has any blood link to the baby.
The 21-year-old, who gave birth to Gammy and his sister in December, told Fairfax Media the egg implanted in her came from a Thai woman and was supplied through a surrogacy agency.
"Yes, the sperm came from (Farnell) but the egg did not belong to the Chinese woman," she said.
Her comments follow a tearful interview given by Mrs Farnell and her husband David, who says his daughter is 100 per cent safe with him despite being convicted for child sex offences.
The couple have custody of Gammy's twin sister, who was brought to Western Australia from Thailand shortly after Pattaramon Chanbua gave birth.
"The sperm came from (Farnell) but the egg did not belong to the Chinese woman."
Pattaramon Chanbua says the couple abandoned Gammy because he has Down syndrome, but they've denied this.
56-year-old David Farnell has told the Nine Network he deeply regrets his child sex offences and the counselling he received in prison has stopped him committing again.
The couple also denied they abandoned baby Gammy.
"We wanted to bring him with us," Farnell said.
"It's been very stressing. We miss our little boy. I come home from work some days and Wendy has our little girl all in blue, because she wants still to remember the little boy."
The couple said after they were told Pattaramon Chanbua was pregnant with twins they were "over the moon" but this changed when they were told late in the pregnancy one had Down syndrome.
By this stage it was too late for an abortion and Farnell said they were angry that tests were not done earlier and they had wanted the surrogacy agency to give them their money back.
However, he denied the couple forced Pattaramon Chanbua to keep the baby.
"I know it sounds very, very heartless, but I never meant to hurt anybody."
"We never agreed to that,” he said.
"We said we want both babies to be born and we will think about this.
"I know it sounds very, very heartless, but I never meant to hurt anybody, like I can't really explain, I can't really put it in words. We never said, ‘you can have this baby'."
The couple said Pattaramon Chanbua threatened that if they took Gammy she would keep both babies and this forced them to leave with only the baby girl.
"She said that if we try to take our little boy, she's going to get the police and she's going to come and take our little girl ... and she's going to keep both of the babies," Farnell said.
However, when questioned about what they had done since leaving Thailand to get Gammy back the couple admitted that so far they had only spoken to Australian authorities to ensure their baby daughter was legally theirs.
The couple contacted their surrogacy agency to send a few thousand dollars to care for Gammy, but admitted they had not contacted anyone about how their son was doing since returning to Australia.
The couple say they intend to return to Thailand once the issues surrounding their daughter are resolved.
